Aluminum electron shield coated with powder of one of iron, copper, nickel and cobalt

ABSTRACT

An improved electron shield for color picture tubes provided in the space between a supporting section of a color selective electrode, such as a shadow mask, and a gas-tight vessel to prevent unnecessary electrons from bombarding the phosphor screen. The material used for the shield is a surface-roughened aluminum sheet with metal powder not larger than 1 Mu in grain diameter deposited in an alloy-like state on one side of an aluminum sheet as a base material. Thus, both the effective area and the thermal radiation of the electron shield are made large, whereby the temperature rise in the shadow mask is reduced to prevent chromatic aberration.

I United States Patent Ezawa 1 Sept. 5, 1972 [54] ALUMINUM ELECTRONSHIELD 2,806,165 9/1957 Law ..313/92 B COATED WITH POWDER OF ONE OF3,392,297 7/1968 Schwartz ..313/92 B IRON, COPPER, NICKEL AND COBALT3,404,303 10/1968 Levin ..313/85 S [72] inventor: Masayoshl Ezawa,Mobara, Japan Primary Examiner Robert Sega] [73] Assignee: Hitachi,Ltd., Tokyo, Japan Attomey-Craig and Antonelli [22] Filed: Oct. 28, 1970[57] ABSTRACT 2 Appl' 84631 An improved electron shield for colorpicturetubes provided in the space between a supporting section of [30] ForeignApplication Priority Data a color selective electrode, such as a shadowmask,

and a gas-tight vessel to prevent unnecessary electrons Oct. 31, 1969Japan ..44/102932 from bombarding the phosphor screen The material d forthe shield is a surface-roughened aluminum [52] US. Cl ..313/85 S 313/41use 51] Int. Cl ..H0lj 29/06, HOlj 31 20, H01 61/52 F f mt F than 1 9[58] Field of Search 313/85 S 92 B 41 diameter deposited in analloy-like state on one side of an aluminum sheet as a base material.Thus, both the effective area and the thermal radiation of the elec- [56"9" cued tron shield are made large, whereby the temperature UNITEDSTATES PATENTS rise in the shadow mask is reduced to prevent chro-2,013,419 9/1935 Moran ..313/41 mm aber'amn' 2,491,284 12/1949 Sears...2 9/198 1 Claim, 2 Drawing Figures 7 INUMELECTKQ SHI CO W H POWDER OFONE OF IRON, COPPER, NICgEL AND COBALT BACKGROUND OF THE INVENTION 1.Field of the Invention This invention relates to improvements in colorpicture tubes, and more particularly to improvements in an electronshield for such tubes.

2. Description of the Prior Art It has heretofore been common practicethat an electron shield for a color picture tube is formed of a metalsheet or foil having glossy surfaces, such as an aluminum sheet or foil.With the prior art electron shield, however, electrons colliding withthe glossy surface are reflected. As a result of this, various problemsare caused such that the proportion of thermal expansion of the shadowmask is increased to bring-about chromatic aberration and the reflectedelectrons which pass through apertures in the shadow mask excite thephosphor screen to emit undesired light.

SUMMARY or THE INVENTION It is accordingly an object of this inventionto provide a color picture tube of an improved construction, which isfree from the various disadvantages mentioned above.

Another object of this invention is to provide a color picture tube inwhich the effective area as well as the thermal radiation of an electronshield is made large, so that a color selective electrode is notaffected by unnecessary electrons.

In accordance with the invention, there is provided a color picture tubecomprising a gas-tight vessel, an electron gun disposed in the gas-tightvessel, a phosphor screen emitting colors upon impingement of electronbeams thereon, and an electron shield preventing unnecessary electronsfrom impinging on the phosphor screen, characterized in that theelectron shield is constructed of a surface-roughened aluminum sheethaving a metal powder formed in an alloy-like state on a surface of thealuminum sheet, one or more kinds of metal powder of iron, copper,nickel, cobalt and the like, which are l p, or smaller in particle size.

Further objects, features and advantages of this invention will becomeobvious from the detailed explanation given hereinbelow with referenceto the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view, partly brokenaway, showing a color picture tube embodying this invention.

FIG. 2 is an enlarged view of pertinent portions in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, numeral1 designates a gastight vessel, 2 an electron gun, 3 a phosphor screen,4 a color selective electrode such as a shadow mask disposed in closeproximity to the phosphor screen 3, 5 a supporting frame for the shadowmask 4, and 6 an electron shield. Details of one form of the electronshield 6 are shown in FIG. 2. More specifically, the shield element 6uses an aluminum sheet as its base material. On one side of the aluminumsheet is stuck at least one kind of metal powder of iron, copper,nickel, cobalt, etc. in the form of fine grains not larger in particlesize than 1 b. The metal powder adhering on the aluminum sheet is bakedat a temperature of approximately 550 to 650 C in a hydrogen furnace.Then, the metal powder is deposited like an alloy on the surface of thealuminum sheet. Thus, a surface-roughened aluminum sheet is formed. Thisis shaped for use into a predetermined configuration. In assemblage, theroughened surface 6a is brought to the side facing the electron gun 2,while the other surface 6b is secured to the supporting frame 5 by anysuitable means such as welding or screw clamping. The space 7 betweenthe supporting frame 5 and the envelope 1 is thus shielded.

There will now be explained a concrete example of the method ofmanufacturing the surface-roughened aluminum sheet for use in theelectron shield for color picture tribes according to this invention. v

To about 63 gof nitrocellulose, ml of diethyl oxalate and 680 ml ofbutyl acetate are added. This mixture is subjected to rolling todissolvethe nitrocellulose. To the rolled mixture are then added about 100 ml ofrape oil and 330 g of iron powder having a grain diameter of .l p. orsmaller, respectively, and these are again subjected to rolling.Thereafter, the material thus twice rolled in applied onto an aluminumsheet. In the next.step, the applied material is dried with eg anultrared lamp. Finally, the aluminum sheet with the dried materialthereon is heated in a hydrogen furnace at about 600C for 5 minutes tothereby finish the manufacture.

The surface-roughened aluminum sheet thus formed is shaped into adesired configuration to obtain the electron shield for a color picturetube.

As described above, the color picture tube according to the inventionhas its electron shield constructed of a surface-roughened aluminumsheet. Accordingly, the effective area as well as the thermal radiationof the electron shield may be increased, since that surface of theshield element on which unnecessary electrons are bombard becomes acolored and roughened one. It is therefore possible to reduce thetemperature rise in the shadow mask and to make its thermal expansionsmaller. In addition, the color picture tube is advantageous from theviewpoint of color purity. It is so excellent in practical use.

I claim:

1. A color picture tube comprising a gas-tight vessel, an electron gundisposed in said gas-tight vessel for generating a plurality of electronbeams, a color phosphor screen disposed in said envelope opposite saidelectron gun for emitting colors upon bombardment by said electronbeams, a shadow mask electrode mounted in said envelope adjacent saidphosphor screen so as to form an annular gap with said envelope, and anelectron shield secured to a supporting section of said color selectiveelectrode for shielding the entire annular gap between said supportingsection and said gas-tight vessel thereby preventing bombardment ofunnecessary electrons onto said phosphor screen, wherein said electronshield is formed of an aluminum sheet having a roughened surface layerarranged on the side facing said electron gun, and wherein saidsurfaceroughened aluminum sheet comprises an aluminum sheet and powderof at least one metal selected from the group consisting of iron,copper, nickel and cobalt, said powder being deposited on at least thesurface of said aluminum sheet facing said electron gun and notexceeding 1 p. in particle size. 5

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